DESCRIPTION Abstract: Using enzymes that possess exquisite and diverse catalytic power, an enormous array of complex natural products (NPs) is synthesized across the different kingdoms. The vast chemical diversity, especially of NPs from plants and microorganisms, contributes to the wide range of useful biological activities displayed by NPs. Collectively, NP and NP-derived drugs have been indispensible towards the treatment of different diseases and the prophylactic maintenance of healthy lifestyle. Due to increasing disease resistance to existing drugs and a dwindling pipeline of new drug leads, our need to generate chemical diversity is becoming ever more important. The best source to mine chemical diversity remains to be from NPs. While traditional, phenotype-based screening of NP from organisms found in esoteric parts of the world continues to be a source of new chemical entities, it has become clear that new approaches using the vast genomic information, as well as powerful tools in chemical biology can be applied towards the rediscovery of natural chemical diversity, starting from the wealth of NP biosynthetic information accumulated to date. Essentially, we believe that many of the microorganisms already identified and cultured contain far more biosynthetic potential than what has been tapped so far, and the manipulation of the known biosynthetic enzymes will lead to even more diversity than currently accessible. In this proposal, we will use two approaches to rediscover the chemical diversity from Nature. First, we will use genomics driven methods to discover the majority of NPs that are encoded, but not synthesized by microorganisms during normal cultivating conditions. Synthetic biology strategies in both the native and heterologous hosts will be developed to fully realize the biosynthetic potential of known organisms. Second, we will develop protein engineering strategy to evolve known biosynthetic enzymes towards generation of new chemical diversity. A three component